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Extraocular muscles

Topic: Anatomy

Created on Tuesday, July 11 2006 by

Last modified on Wednesday, December 31 1969.

A 112 year-old male harrier keeper visits you in a shack near the base of Mt. Everest, complaining of diplopia.
You note that most of the time that he is facing you and talking, he sits with his chin turned toward his right shoulder and his right eye abducted.
Based on this information alone, you suspect that there may be a paresis of which extraocular muscle?

A) Left medial rectus

B) Right lateral rectus

C) Right superior oblique

D) Left lateral rectus

E) Right inferior oblique

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This question was created on July 11, 2006 by .
This question was last modified on December 31, 1969.

ANSWERS AND EXPLANATIONS

A) left medial rectus

This answer is correct.

This presentation is typical of a paresis of the left medial rectus. A patient with a paresis of the left medial rectus muscle will have impaired adduction of the left eye, and is likely to try to minimize his diplopia by looking at the world with his chin turned toward his right shoulder and his right eye abducted. (See References)


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B) right lateral rectus

This answer is incorrect.

This presentation is typical of a paresis of the left medial rectus. A patient with a paresis of the right lateral rectus muscle will have impaired adbuction of the right eye, and is likely to try to minimize his diplopia by looking at the world with his chin turned toward his right shoulder and his left eye adducted. (See References)


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C) right superior oblique

This answer is incorrect.

This presentation is typical of a paresis of the left medial rectus. A patient with a paresis of the right superior oblique muscle will have impaired depression and inward rotation of the right eye, and is likely to try to minimize his diplopia by looking at the world with his chin held down and his head tilted and turned with his left ear held close to his left shoulder. (See References)


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D) left lateral rectus

This answer is incorrect.

This presentation is typical of a paresis of the left medial rectus. A patient with a paresis of the left lateral rectus muscle will have impaired adbuction of the left eye, and is likely to try to minimize his diplopia by looking at the world with his chin turned toward his left shoulder and his right eye adducted. (See References)


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E) right inferior oblique

This answer is incorrect.

This presentation is typical of a paresis of the left medial rectus. Paresis of the right inferior oblique muscle does not present in this way. (See References)


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References:

1. Ross, R.T. (1999). How to Examine the Nervous System, 3rd Edition. Appleton & Lange, Stamford, Connecticut. Pp. 45-60


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anatomy
Extraocular muscles
Question ID: 0000003
Question written by . (C) FrontalCortex.com 2006-2009, all rights reserved. Created: 07/11/2006
Modified: 12/31/1969
Estimated Permutations: 0